In its simplest form, an optical waveguide is an interconnect medium represented by two regions of different refractive index. The core region of a waveguide is represented by the region of higher refractive index, while the cladding region is represented by the region of lower refractive index. For confinement and guiding of optical energy to occur, the region of high refractive index must be surrounded by the region of lower refractive index.
To create this contrast in refractive index, Δn, between core and cladding regions, optical waveguides are made using a variety of methods and materials. Previous fabrication techniques include molding, embossing or casting (U.S. Pat. Nos. 6,272,275 and 6,233,388), photo-bleaching (U.S. Pat. No. 5,708,739), aerosol deposition (U.S. Pat. No. 5,622,750), lamination (U.S. Pat. No. 5,5407,990), guttering (U.S. Pat. No. 5,196,041), laser-writing (U.S. Pat. No. 4,949,352), metal (U.S. Pat. No. 4,284,663) and ion (U.S. Pat. Nos. 5,160,523, 5,114,453, 6,226,433, 5,979,188) diffusion and doping (U.S. Pat. No. 5,080,931), and thermal diffusion (U.S. Pat. Nos. 5,194,079 and 5,551,966), for example.
Waveguides made from optical polymer materials are of particular interest due to their low cost and ease of manufacture (K. Glukh, et al, Proc. SPIE Linear, Nonlinear, and Power-limiting Organics, 43-53, August 2000) with respect to integration within gigascale (GSI) microelectronics (International Technology Roadmap for Semiconductors, 2001 update). One limitation of polymer materials, however, which restricts the maximum waveguide density and minimum bending radius of an optical waveguide pathway is the low refractive index contrast between process-compatible core and cladding materials. Typical values for Δn are low within polymer technologies (e.g., Δn=0.03) (K. Glukh, et al., Proc. SPIE Linear, Nonlinear, and Power-limiting Organics, 43-53, August 2000). A high Δn increases confinement of optical energy within the core region, which in turn allows for higher waveguide densities due to the reduction in optical crosstalk and smaller radii bent waveguide paths.
Interconnect density constraints imposed by GSI microelectronics are such that high Δn waveguide technologies (Δn>0.1) are required for chip-level integration (U.S. Pat. No. 6,324,313) of optical waveguides. For the purposes of intra-chip optical data interconnection, for example, a waveguide technology that simultaneously allows for high Δn and low-neff is required to exceed the performance of alternate electrical-interconnect technologies.
Thus, a heretofore unaddressed need exists in industries employing optical waveguide technology to address the aforementioned deficiencies and/or inadequacies.